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Diffstat (limited to 'Documentation/userspace-api/media/v4l/func-mmap.rst')
| -rw-r--r-- | Documentation/userspace-api/media/v4l/func-mmap.rst | 18 |
1 files changed, 7 insertions, 11 deletions
diff --git a/Documentation/userspace-api/media/v4l/func-mmap.rst b/Documentation/userspace-api/media/v4l/func-mmap.rst index b3a9cd862a7f..e3e5e64ebe7e 100644 --- a/Documentation/userspace-api/media/v4l/func-mmap.rst +++ b/Documentation/userspace-api/media/v4l/func-mmap.rst @@ -1,4 +1,5 @@ .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L .. _func-mmap: @@ -11,7 +12,6 @@ Name v4l2-mmap - Map device memory into application address space - Synopsis ======== @@ -20,9 +20,7 @@ Synopsis #include <unistd.h> #include <sys/mman.h> - .. c:function:: void *mmap( void *start, size_t length, int prot, int flags, int fd, off_t offset ) - :name: v4l2-mmap Arguments ========= @@ -54,7 +52,7 @@ Arguments #. The Linux ``videobuf`` kernel module, which is used by some drivers supports only ``PROT_READ`` | ``PROT_WRITE``. When the driver does not support the desired protection, the - :ref:`mmap() <func-mmap>` function fails. + :c:func:`mmap()` function fails. #. Device memory accesses (e. g. the memory on a graphics card with video capturing hardware) may incur a performance penalty @@ -70,7 +68,7 @@ Arguments ``MAP_FIXED`` requests that the driver selects no other address than the one specified. If the specified address cannot be used, - :ref:`mmap() <func-mmap>` will fail. If ``MAP_FIXED`` is specified, + :c:func:`mmap()` will fail. If ``MAP_FIXED`` is specified, ``start`` must be a multiple of the pagesize. Use of this option is discouraged. @@ -87,7 +85,7 @@ Arguments flags. ``fd`` - File descriptor returned by :ref:`open() <func-open>`. + File descriptor returned by :c:func:`open()`. ``offset`` Offset of the buffer in device memory. This must be the same value @@ -97,11 +95,10 @@ Arguments in the struct :c:type:`v4l2_plane` ``m`` union ``mem_offset`` field for the multi-planar API. - Description =========== -The :ref:`mmap() <func-mmap>` function asks to map ``length`` bytes starting at +The :c:func:`mmap()` function asks to map ``length`` bytes starting at ``offset`` in the memory of the device specified by ``fd`` into the application address space, preferably at address ``start``. This latter address is a hint only, and is usually specified as 0. @@ -111,13 +108,12 @@ Suitable length and offset parameters are queried with the allocated with the :ref:`VIDIOC_REQBUFS` ioctl before they can be queried. -To unmap buffers the :ref:`munmap() <func-munmap>` function is used. - +To unmap buffers the :c:func:`munmap()` function is used. Return Value ============ -On success :ref:`mmap() <func-mmap>` returns a pointer to the mapped buffer. On +On success :c:func:`mmap()` returns a pointer to the mapped buffer. On error ``MAP_FAILED`` (-1) is returned, and the ``errno`` variable is set appropriately. Possible error codes are: |